Deliverability is whether your email reaches the inbox rather than the spam folder, or nowhere at all. For cold outreach it's the foundation everything else sits on. Gmail, Outlook and other mailbox providers judge every sender on how it's set up and how it behaves, and they're quick to filter senders that look careless.
Nobody can guarantee every email reaches every inbox. But the steps below are what careful senders do, and they make a large difference.
Authenticate your domain: SPF, DKIM and DMARC
Authentication proves to receiving servers that you're allowed to send email for your domain. Without it, your email looks like it could be forged. There are three records to set up in your domain's DNS:
- SPF (Sender Policy Framework) lists the servers allowed to send email for your domain. If you send through a provider such as Google Workspace or Microsoft 365, they'll give you the value to add.
- DKIM (DomainKeys Identified Mail) adds a cryptographic signature to each email, so the receiver can check it came from your domain and wasn't altered on the way.
- DMARC tells receivers what to do if an email fails SPF and DKIM checks, and lets you receive reports. Start with a monitoring policy (
p=none) and tighten it once you're confident all your legitimate email passes.
Make sure the domain in your From address aligns with the domain that passes SPF or DKIM. Your email provider's setup guide will walk you through each record.
Use a separate sending domain for outreach
Many businesses send cold outreach from a secondary domain, such as a variation of their main brand name, rather than their main company domain. The reason is risk: if outreach ever damages a domain's reputation, you don't want it to be the domain your customers, invoices and supplier emails rely on.
A secondary domain needs the same care as your main one. Set up SPF, DKIM and DMARC, point its website at your main site so recipients can see who you are, and warm it up before sending at volume.
Warm up new domains and mailboxes slowly
A brand-new domain or mailbox has no reputation. If it suddenly sends hundreds of emails a day, providers treat that as a warning sign. Instead, build volume gradually:
- Start with a small number of emails a day.
- Increase steadily over several weeks, watching bounces and replies as you go.
- Hold or reduce volume if bounces or complaints rise.
Consistency matters as much as the numbers. A steady pattern looks like a real person working through their day; sudden spikes don't.
Send at a human pace, in business hours
How you send is as important as what you send. Good habits for B2B outreach:
- Send during the working day, Monday to Friday, when people are at their desks.
- Spread emails out rather than sending a batch all at once.
- Vary daily volume a little, the way a person's would.
- Never email the same person twice from different lists or companies. One director of several companies should hear from you once.
Keep bounces low by verifying addresses
A bounce happens when an email can't be delivered, usually because the address doesn't exist. A high bounce rate is one of the clearest signals of a careless sender, because it suggests the list was bought, scraped or guessed.
- Verify every address before you send to it.
- Don't send to guessed addresses you haven't checked.
- Remove addresses that hard bounce immediately and never send to them again.
- Pause sending if bounces start rising, and find out why before resuming.
Our guide to finding a company director's email address covers verification in more detail.
Spam complaints and unsubscribes
When a recipient marks your email as spam, the provider counts it against you. Complaints do far more damage than people simply ignoring you, so it pays to make leaving easy.
Google and Yahoo's sender requirements
In 2024 Google and Yahoo introduced requirements for anyone sending to their users. All senders need to authenticate their email and keep spam complaint rates low; Google asks senders to stay below 0.3%, and recommends staying well under 0.1%. Bulk senders, which Google defines as those sending around 5,000 or more messages a day to Gmail addresses, must also have SPF, DKIM and DMARC in place, and must support one-click unsubscribe for marketing messages and honour unsubscribes promptly. Microsoft introduced similar authentication requirements for high-volume senders to its consumer email services in 2025. See Google's email sender guidelines for the current details.
One-click unsubscribe
One-click unsubscribe is defined in RFC 8058. It uses the List-Unsubscribe and List-Unsubscribe-Post email headers so mail apps can show an unsubscribe button next to your name. Even if you send far below bulk volumes, including it is good practice: someone who can unsubscribe easily is less likely to hit "report spam". Honour every unsubscribe instantly and permanently. It's also part of staying within the rules covered in our guide to cold email law.
Write emails that look like they came from a person
- Keep formatting simple. A short, mostly plain-text email reads like one person writing to another. Heavy HTML templates, large images and banners look like marketing.
- Limit links. One link, to your own domain, is plenty. Avoid link shorteners.
- Be personal and relevant. Use the person's name and say why you're writing to their business specifically.
- Think about tracking. Open and click tracking rely on images and rewritten links. They're useful for spotting interested prospects, but use a tracking domain that's properly set up and aligned with your sending domain.
- Avoid spammy language such as all-caps subject lines and excessive punctuation.
Monitor your reputation
Keep an eye on how you're doing so you can act before a problem grows:
- Bounce and complaint rates from your own sending data.
- Reply rates. A sudden drop can be an early sign emails are going to spam.
- Google Postmaster Tools, which shows Gmail's view of your domain, including spam rate and authentication results, once you send enough volume to Gmail users.
- DMARC reports, which show whether your email is passing authentication.
How Pucky builds these habits in
Pucky sends personal emails gradually in business hours, checks each address can receive mail before sending, warms new accounts up slowly and pauses outreach automatically if too many emails bounce or anyone reports spam. Every email includes one-click unsubscribe. On the Professional plan, Pucky manages dedicated secondary sending domains for you. See sender reputation protection and email outreach.
Frequently asked questions
Why are my cold emails going to spam?
Common causes are missing SPF, DKIM or DMARC records, sending too much from a new domain, high bounce rates from unverified addresses, spam complaints and emails that look like mass marketing. Fix authentication first, then slow down and clean your list.
Do I need DMARC for cold email?
Yes, it's strongly recommended. Google and Yahoo require DMARC for bulk senders, and having it in place helps prove your email is genuine whatever your volume.
How long does it take to warm up a new domain?
There's no fixed rule, but it usually takes several weeks of gradually increasing volume. Watch bounces and replies, and only increase volume while they stay healthy.
What spam complaint rate is too high?
Google asks senders to keep their spam rate below 0.3% and recommends staying under 0.1%. For cold outreach, aim to keep complaints as close to zero as possible.